Hydroformylation of olefins and reductive carbonylation of aryl halides with syngas formed ex situ from dehydrogenative decarbonylation of hexane-1,6-diol

Abstract

A variety of primary alcohols have been investigated as convenient substrates for the ex situ delivery of carbon monoxide and molecular hydrogen in a two-chamber reactor. The gaseous mixture is liberated in one chamber by an iridium-catalysed dehydrogenative decarbonylation of the alcohol and then consumed in the other chamber in either a rhodium-catalysed hydroformylation of olefins or a palladium-catalysed reductive carbonylation of aryl halides. Hexane-1,6-diol was found to be the optimum alcohol for both reactions where moderate to excellent yields were obtained of the product aldehydes. A relatively low pressure of 1.5-2.4 bar was measured in the closed system during the two transformations.

Ruthenium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

“…Recently, we presented a thorough mechanistic study of the iridium‐catalyzed dehydrogenative decarbonylation where the reaction was shown to go through two catalytic cycles (dehydrogenation and decarbonylation) with the square‐planar complex IrCl(CO)BINAP as the catalytically active species in both cycles . The [Ir(COD)Cl] 2 /BINAP system was also used for releasing dihydrogen and carbon monoxide, i.e., syngas, from diols and polyols in a two‐chamber system where the liberated syngas was utilized for hydroformylation of olefins or reductive carbonylation of aryl halides in the second chamber …”

Continuous‐flow Synthesis of Aryl Aldehydes by Pd‐catalyzed Formylation of Aryl Bromides Using Carbon Monoxide and Hydrogen

“…In particular, 9‐methylfluorene‐9‐carbonyl chloride was employed to generate stoichiometric amounts of CO and potassium formate as the hydride source within a two‐chamber system (COware) for reductive carbonylation of aryl iodides . Madsen and co‐workers also demonstrated a two batch chamber configuration for the ex situ formation of CO and H 2 using an iridium‐catalyzed dehydrogenative decarbonylation of hexane‐1,6‐diol, which was fed into a second chamber for the formylation of aryl bromides . The Ley group pioneered the tube‐in‐tube reactor gas‐loading concept to enable the safer introduction of gases into the liquid‐phase from gas cylinders .…”

“…[11] Madsen and co-workersa lso demonstrated at wo batch chamber configurationf or the ex situ formationo fC O and H 2 using an iridium-catalyzed dehydrogenative decarbonylation of hexane-1,6-diol, which was fed into asecond chamber for the formylation of aryl bromides. [12] The Ley group pioneered the tube-in-tube reactor gas-loading concept to enable the safer introduction of gases into the liquid-phase from gas cylinders. [13] Teflon AF-2400 (a fluoropolymer) is used as as emipermeable membrane, which is permeable to gases but impermeable to liquids.…”

Heterogeneous Phase Microwave-Assisted Reactions under CO2 or CO Pressure

“…Despite the above-mentioned advantages, CO’s reputation as “the silent killer” that leads to asphyxiation (as an oxygen competitor in haemoglobin binding), has generated major concern and warnings concerning its use. A number of protocols that see CO released in situ have been developed to circumvent the safety issues surrounding this invisible, odourless, tasteless and highly toxic gas [13,14,15,16,17,18,19]. These methods include the use of CO-equivalents (alkyl formates [20], formic acid, formic anhydride, formamide [21,22,23], N -substituted formamide [24], carbamoylstannanes [25], carbamoylsilane [26]), and CO-releasing reagents (metal carbonyls [27]).…”